The invention relates to a self-illuminating LCD display device.
It is known, for example, from the article Displaysxe2x80x9d by R. J. Visser in Philips J. Res. 51 (1998) 467-477, to illuminate LCD display devices by backlighting using planar polymeric light-emitting diodes. This illumination can be used, on the one hand, to intensify the contrast when the display device is used in daylight, and on the other hand to illuminate the display device in darkness.
The use of two modules has, however, the disadvantage that there is a need for additional mounting steps which are, in addition, very difficult to execute since the two planar elements must be designed in a very flat fashion and aligned exactly parallel to one another, in order, for example, to avoid the formation of Newton rings.
U.S. Pat. No. 3,811,751 discloses a self-illuminating LCD display device which has an LCD layer and a flat electroluminescent element as backlighting, between which there are located two layers of a film for influencing the light emitted by the electroluminescent element and having strip-shaped microstops inclined with respect to the perpendicular serve the purpose of deflecting the light emitted by the electroluminescent element such that when viewed in a direction perpendicular to the surface of the LCD display device, the background appears dark and only light deflected by LCD pixels passes to the observer. However, the contrast is reversed from other, lateral directions of view.
It is the object of the invention to provide a self-illuminating LCD display device which is easy to produce and mount and whose viewing angle range is determined by the actual LCD layer.
The object is achieved by means of an LCD display device having the features of claim 1.
The polarizer layers of the LCD module can be arranged on the side of the appropriate substrate averted from the liquid crystal layer, or between the substrates of the module and the electrode layers.
The idea of using the polarizer facing the backlighting or, when the polarizer is arranged between the electrode layer and substrate, of using the substrate of the LCD module facing the backlighting as substrate for the transparent electrode of the LED module eliminates problems in connection with the planeness and the accuracy of fit of the surfaces of the illumination unit. Moreover, one substrate less is used. Finally, the mounting steps for assembling the elements are eliminated.
Except for the arrangement of the third electrode layer, the LCD module and the LED module can be designed in a fashion corresponding to the prior art.
Apart from that, any desired materials can be used as organic light emitting materials, light emitting polymers being preferred.
Advantageous developments of the invention are defined in the subclaims.
A self-illuminating LCD display device according to the invention preferably has a sealing element which is arranged like a frame along the circumference of the surface of the LCD module between the first transparent substrate and the second transparent substrate or solid layers respectively arranged thereon. Likewise, it is advantageous for the purpose of lengthening the service life of the light emitting layer when a sealing element is arranged like a frame along the circumference of the surface of the LED module between the second transparent substrate and the third substrate or solid layers respectively arranged thereon, with the result that the interior is enclosed in an airtight and watertight fashion.
The transparent electrode layers are preferably formed by indium zinc oxide layers (ITO layers).
The transparent substrates are preferably glass plates.
The fourth electrode layer can contain suitable metals, for example aluminum or calcium.
In order to increase the luminescence efficiency in the direction of the LCD layer, the metal layer is preferably designed such that it reflects the emitted light. Alternatively, it is possible for a further reflecting layer to be arranged behind the metal layer, or for the substrate to be made from appropriately reflecting material.
A transparent display device is obtained if the fourth electrode layer and a third substrate are of transparent design.
The LED module can contain, between the electrode layers, still further layers which are known to the person skilled in the art and improve the functioning of this module. A polymeric protective layer is preferably arranged between the transparent electrode layer in the LED module and the layer with organic light emitting materials, in order to lengthen the service life.
The LED module is preferably designed to represents regions of different color, which can be done, for example, by forming appropriately driveable regions with the aid of organic materials emitting light of different colors.
It is preferred, furthermore, for the layer with organic light emitting materials to have a strip structure the layer with organic light-emitting materials having a strip structure in which at least two types of strips are arranged alternately, and strips of one type respectively have organic light emitting materials which emit light of a specific color, it being possible to achieve suitable, mixing of the emitted light. It is particularly preferred for the strips to be so narrow that they cannot be resolved by the human eye from a typical viewing distance.
It is preferred in this case that the third or the fourth electrode layer is structured in accordance with the strip structure for the purpose of driving the strip of one type in each case, such that the color of the backlighting can be varied by the drive. By contrast with polychromatic matrix displays which are used to produce light of mixed colors, only one electrode need be structured in order to produce light of mixed colors.
During operation, the strips are driven such that light of a desired color is emitted. The second transparent substrate can be designed as a diffusing screen for better mixing of the light.
It is particularly preferred to use at least three types of strip whose organic light emitting materials are selected such that with suitable driving the mixing of the emitted light of the strips yields white light.
If, in this case, the width of the strips corresponds to the size of the pixels of the LCD module, and if the strips are aligned with these pixels, it is possible in a particularly preferred fashion to implement a self-illuminating, color display device, in particular with simultaneous operation of all types of strips. This requires the LCD module to be designed only as a monochromatic display device except for the drive. Driveable color filters in the LCD module can be dispensed with entirely.
In this case, the arrangement of the second and third ITO layers eliminates difficult subsequent adjustment of the LED module with the LCD module in the case of a simple combination of an LCD module with a separate LED module.
The LCD module can, however, also be designed for displaying polychromatic displays in conjunction with monochromatic or white illumination. In this embodiment, an exact alignment of pixels of the LCD module and strips of the LED module is superfluous, particularly when use is made of an LED module with strip structure.